Research On Enhanced Coagulation Process Of The Chemical Fiber Wastewater

Wastewater comes from wet process producing acrylic fiber contains large amounts ofpolymer,oligomer or mixture of acrylonitrile monomer,which is hardly biodegradable and hasstrong adhesion,so it is easy to be wrapped in soft filler in anaerobic and aerobic tank afterlong time running and destroy the biofilm.Wastewater containing aldehydes,cyanide,benzeneand other toxic substances is easy to produce toxic effects on microorganisms,therefore,thechemical pretreatment of wastewater, improving water quality and improving thebiodegradability of wastewater have practical significance on chemical treatment effect andmeeting wastewater discharge standards.Laboratory simulation water or chemical fiber wastewater and practical wastewater froma chemical plant in Jilin or chemical fiber raw water were treated as the experimental subjects.PAC,polymeric ferric chloride,aluminum sulfate and ferric sulfate were chosed ascoagulant,polyacrylamide,magnesium oxide,magnesium sulfate,silver nitrate were treated ascoagulant aids, potassium permanganate,potassium ferrate,a new eco-iron,iron-carbonmicroelectrolysis pre-oxidants were as preoxidation reagents.Samples were treated bycoagulate,coagulate+coagulation aid,pre-oxidation+coagulate,coagulation aid+pre-oxidation+coagulate and enhanced coagulation,and they explored various treatment mehtods and theireffects on the removal of COD in water samples and turbidity removal.Experiments showsthat coagulation and enhanced coagulation treatment both have good results on removalefficiency for chemical fiber wastewater COD and turbidity,which is worse for chemical rawwater.The results shows four kinds of coagulant aids and coagulants have certain effect onremoving COD and turbidity by using coagulant only coagulation process to deal withsamples..But when handling water distribution polymerization aluminium sulfate ascoagulant, the best reaction conditions is the polymerization of aluminum sulfate20mg/L,reaction pH=6,30s, and medium speed fast stirring3min, slowly mixing5min, then stand for10min.Effluent turbidity removal rate is78%, the COD removal rate is82%. Thetreatment effect is best when handling chemical fibber raw water with polyaluminiumchloride as coagulant,and add polyaluminium chloride70mg/L,keep pH=9, fast mixing30s,medium-speed stirring3min, slowly mixing5min, and then stand for10min.The waterturbidity removal rate is34%and COD removal rate is15%.The results shows four kinds of coagulant aids and coagulants have certain effect onremoving COD and turbidity by using coagulant aids together enhanced coagulation processto deal with samples. But the effect is best when handling water distribution with silver nitrateas coagulant aid and polymeric ferric sulfate as coagulant removal effect, the optimal reactioncondition is silver nitrate dosing quantity25mg/L, polymeric ferric sulfate dosing quantity50mg/L, reaction pH=4and fast mixing30s, medium-speed stirring3min, slowly mixing5min, and then standing for10min.Effluent turbidity removal rate is18%, the COD removalrate is95%.And the removal effect is best when handling chemical fibber raw water withmagnesium oxide as the coagulant aid and polymeric ferric sulfate as the coagulant, the bestprocessing condition is magnesium oxide10mg/L, polymeric ferric sulfate50mg/L, pH=4,and fast mixing30s, medium-speed stirring3min, slowly mixing5min, and then standingfor10min.Effluent turbidity removal rate is85%, the COD removal rate is30%.The results shows four kinds of coagulant aids and coagulants together have effect onremoving COD and turbidity by using preoxidation strengthening coagulation method to dealwith samples.But the removal effect is best when iron carbon micro electrolysis oxidized andpolymerization ferric chloride as the coagulant, the optimum reaction condition throughorthogonal test is iron carbon micro electrolysis pH=3, sponge iron and activated carbonadditive quantity5g/L, PAM dosing quantity25mg/Land20min reaction time, coagulationpH=9, polymeric ferric chloride dosing quantity50mg/L, fast mixing40s, medium-speedstirring4min, slowly mixing6min, and then stand for15min.Through experiments, CODremoval rate is98.36%. The optimum processing conditions are the same for raw wate. Waterturbidity removal rate is21.26%and the COD removal rate is38.23%.Quality both of chemical fiber wastewater and chemical fiber raw water treated byenhanced coagulation improved to some extent.COD and turbidity decreased andbiodegradability increased. However, the effect in fiber raw water is not as good as in thechemical fiber water, because of high potential and strong stability in the chemical fiber waterand it is more stable and not easy to treat.It can be seen from the molecular weight.Chemicalfiber raw water have more small molecules and they are more evenly dispersed, and they arenot easy to be damaged. So enhanced coagulation just can improve the biochemical ratio,change the nature of colloids and improve its biodegradability, In order to make thewater quality meet standard completely, the further biological treatment is necessary.